By 'doesn't work', do you mean nothing shows up on the screen when you turn your PS3 on?
All you gotta do is keep holding down the power button on the front of the PS3 when you use it to turn it on. After ~5 seconds you'll hear a beep. Let off the button and wait a second and a message will pop up on the screen to change your graphics to optimal settings. If its currently hooked up with HDMI, it'll automatically change over for you.







